I did add an a4j:log to the page. When I specify the event as anything other than change I can see the events firing within the log component. When the event attribute is specified nothing is displayed in the a4j:log component. I am adding values to the selected list, removing them, changing focus to different components even submiting the form. As long as the event is :change" it does not seem like the ajax events are firing.

Brian you suggestion was very helpful adding an onchange event handler on the component does not produce any effect. onchange="alert('Changed');" does nothing while onclick="alert('Clicked');" behaves as expected. I will try and determine if a bug has been submitted for this already.

Replaced 'change' event with 'additems, removeitems, sourceblur, sourcefocus, targetblur and targetfocus' events and it worked for me. There could be some redundant code in this temporary fix but it solved the problem at least. Suggestions are always welcome. Thanks.